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ABSTRACT

A body implantable lead having a two-piece stylet. An inner solid portion of the stylet enables a shape to be imparted to the stylet to allow proper maneuvering of the lead during implant. A second portion of the stylet is slideably located coaxially about the first portion. The second portion of the stylet permits the imposition of a torque at the distal end of the implantable lead by the turning of a knob fixedly attached to the proximal end of the second portion of the stylet. The second portion of the stylet is a helically wound coil. The two-piece stylet is inserted into the proximal end of the body implantable lead. The distal end of the body implantable lead is located in the position desired through the use of the solid inner first portion of the stylet in which a bend or other desired shape has been introduced. The body implantable lead is permanently attached to the muscle tissue by a fixation device activated through the torque supplied by the second portion of the stylet. The two portions of the stylet may be fabricated from a variety of materials.

CROSS-REFERENCE TO CO-PENDING APPLICATION

Attention is drawn to the following commonly assigned co-pending patentapplication:

Flexible Tip Stiffening Stylet for Use With Body Implantable Lead byDutcher et al, Ser. No. 1,203, filed Jan. 5, 1979 now abandoned in favorof continuing application Ser. No. 176,410, filed on Aug. 8, 1980.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates generally to electrical devices formedical application, and more specifically relates to chronicallyimplantable electrodes.

2. Description of the Prior Art

The use of a solid inner stylet to guide the insertion and properplacement of a more flexible coaxial outer catheter is known. Examplesof this art may be seen in U.S. Pat. No. 4,020,829, issued to Willson etal. and U.S. Pat. No. 4,215,703, also issued to Wilson. These referencesteach the guiding of the flexible catheter using such a solid innerstylet wire. To accomplish the desired result, a solid inner stylet wireis given a permanent bend or other shape which causes the catheter to beso bent upon insertion of the inner stylet.

Also common is the use of a stylet for straightening a catheter-likedevice, which itself has been permanently impressed with a bend or otherdesired shape. This is particularly prominent in pacing leads or otherelectrode applications. Examples of electrodes having a predeterminedshape may be found in U.S. Pat. No. 3,890,977, issued to Wilson and U.S.Pat. No. 4,136,703, issued to Wittkampf. These references teach thebuilding of an implantable lead with particular reference to a "J" shapefor insertion within the atrium of a human heart. The electrodes taughtby Wilson and Wittkampf apparently use only the resiliency of the leaditself to maintain contact between the electrode and the stimulatabletissue. Insertion of these "J"-shaped leads is greatly facilitatedthrough the use of a solid inner stylet which, in this case, tends tohave a straightened shape for straightening the bend normally fixedwithin the distal end of the lead.

Leads having positive fixation means are also known in the art.Endocardial leads having a helical fixation means are taught in U.S.Pat. Nos. 4,146,036 4,209,019 and 4,217,913 all issued to Dutcher, etal. Each of these references teaches a body implantable lead fortransvenous implantation primarily oriented to implantation within theright ventricle. A stiffening stylet is used to aid in implantation.Torque applied to the stylet is used for fixedly attaching the helicalfixation means. In each case, however, the lead must be disposed in anearly straight fashion and the stiffening stylet used must be nearlystraight to enable proper imposition of torque by twisting motion of thestylet.

It has been shown to be desirable to implant a lead such as taught inthe Dutcher references discussed above within the right atrium. The mostdesirable implantation attitude would involve fixation of the helicalfixation means in the right atrial appendage. A "J" shape could beimparted to the implantable lead by using a shaped stylet as taught byWillson, et al. in the references discussed above, or by shaping thelead itself as taught in the references by Wilson and Wittkampf. Shapingthe stylet would tend to cause difficulty in transmitting torque fromthe proximal and distal ends of the stylet to enable attachment of thefixation means. In fact, if one would take the stylet taught in theDutcher references above and impart a "J" shape to it, it would becomeno longer useful for attaching the helical fixation means.

Shaping the body implantable lead using memory coils or other techniquesas taught by Wilson and Wittkampf would allow the stylet to impart thenecessary torque. However, this technique is disadvantageous because itmakes fabrication of the lead relatively more expensive and increasesthe handling difficulty because the stylet is normally much stiffer thanthe body of the implantable lead. This means that the stylet, afterbeing inserted for the purposes of attaching the helical fixation means,would tend to remove the "J" shape from the body of the implantablelead.

SUMMARY OF THE INVENTION

The present invention overcomes these difficulties through the use of atwo-piece stylet. The two-piece stylet is inserted within a bodyimplantable lead such as is taught the Dutcher references. A first,inner portion of the stylet is a solid stiffening wire. This innerportion is shaped by the implant physician in the desired manner, toprovide for easy implantation. For most atrial applications, this shapewill be a "J" or modified "J". The "J" shape will allow for attachmentat the desired position within the atrial appendage. Depending upon theexact implantation technique used, a second solid stylet wire may beused first to locate the distal end of the implantable lead within theatrium. This would ease the transvenous insertion process. The shapedstylet would then be inserted to insure that the distal end of theimplantable lead assumes a "J" shape.

The second portion of the stylet is a helically wound coil which isfitted coaxially outside of the first solid portion. Because of its coilshape, the second portion of the stylet is much more flexible andtherefore, does not determine the shape of the distal end of theimplantable lead as does the first portion. The function of the secondportion of the stylet is to enable the transmission of a torque appliedby the implant physician at the proximal end to be transmitted to thehelical fixation means located on the distal end of the lead. Thetransmission of this torque allows the helical fixation means to bescrewed into the endocardial tissue. Notice that, because of thisflexibility, the second portion of the stylet will allow this torque tobe transmitted notwithstanding the shape chosen for the inner solidportion.

The combined two-piece stylet taught herein is inserted within thecentral lumen of the body implantable lead in the normal fashion. Noticealso that the second portion of the stylet may be shaped instead toimpart a desired curvature to the distal end of the lead. This can beaccomplished using memory coil technology. It is necessary however, thatthe torque transmitting portion of the stylet be substantially moreflexible than the shaping portion.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a prior art endocardial lead having helical fixation meansusing a prior art stylet.

FIG. 2 is a plan view of the first inner portion of the improved stylet.

FIG. 3 is a plan view of the second outer portion of the stylet.

FIG. 4 is an end view of the proximal end of the second outer portion ofthe stylet.

FIG. 5 is an end view showing the distal end of the second outer portionof the stylet.

FIG. 6 is a cross-sectional view of the assembled stylet.

FIG. 7 is an assembled view of the body implantable lead with thetwo-piece stylet inserted.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Whereas the present description concentrates primarily upon a bodyimplantable lead having a two-piece stylet wherein the first innerportion is one which imparts the desired shape to the implantable lead,and the second outer portion of the stylet is used for the transmissionof torque from the proximal to the distal end, those of ordinary skillin the art will readily appreciate that the functions of the inner andouter portions of the stylet may be reversed. To do so, is well withinrealm of present technology although it would appear that this wouldrender an embodiment of the present invention which is less desirablebecause it would be more costly.

FIG. 1 is a plan view of a body implantable lead with stiffening styletinserted. This body implantable lead is known in the prior art as taughtby Dutcher, et al in U.S. Pat. No. 4,217,913 which is incorporatedherein by reference. As explained therein, body implantable lead 10 hasa proximal end with electrical connector 14 and terminal pin 12 which isconnected via conductor coil 24 to the ring electrode and separate,electrically isolated fixation means 16 located at the distal end. Themain body of the lead is covered with outer sheath 26 as shown.Stiffening stylet 30 is a solid piece of wire such as stainless steel,which is connected to torque receiving body 28 at position 22. As theimplant physician turns knob 20, this torque is transmitted via styletwire 30 to helical fixation means 16 which is screwed past fixed member11 causing sharpened tip 18 to become fixedly engaged within theendocardial tissue.

FIG. 2 shows the solid inner portion of an improved stylet. Again,stylet knob 20 is attached at the proximal end of stylet wire 30.Different from the prior art, however, distal end 34 is foreshortenedsuch that, if implanted within the body implantable lead (see also FIG.1), distal tip 34 would not reach torque receiving body 28. In additionto being foreshortened, solid stylet wire 30 is also shaped to contain abend at reference 32. This bend is preferably "J" shaped for insertionof the body implantable lead into the atrium. However, other shapes maybe found desirable for other applications.

FIG. 3 shows the second outer portion of the improved stylet. The mainbody of the second portion of the stylet is a flexible, torquetransmitting member (e.g., tube, coil, etc.). Coil 40, used in thepreferred embodiment, is arranged helically and has an inner lumen forthe insertion of the stylet wire 30 (see also FIG. 2). Coil 40 may be ofa variety of materials. It has been found that stainless steel and bodycompatible organic plastics have both proven satisfactory.

The proximal end of coil 40 is attached to stylet housing 36. This isenlarged to create knob 38, having knurled portions 46 as shown. As iscommon in the manufacture of stylets, the proximal portion 36 and knob38 may be constructed of conveniently compatible plastic material. Thedistal end of coil 40 contains torque transmission tool 44. This isshaped for proper insertion into torque receiving body 28 at position 22(see also FIG. 1). Torque transmission tool 44 is welded or attached inanother suitable manner at position 42 as shown.

FIG. 4 is an end view of the proximal end of knob 38. Lumen 50 issufficiently large for the insertion of solid stylet wire 30 (see alsoFIG. 2). Funnel-shaped depression 48 surrounds lumen 50 to greatlyfacilitate insertion of distal tip 34 of solid stylet wire 30.

FIG. 5 is an end view of the distal end of the second portion of theimproved stylet. As can be seen, torque transmission tool 44 has arectangular cross section for transmitting torque to torque receivingbody 28. Torque transmission tool 44 is attached at position 42 asmentioned above by welding or other suitable attachment means.

FIG. 6 is a cross-sectional view of the two-piece stylet as assembled.Notice that distal tip 34 of solid stylet wire 30 is foreshortened.Notice also that torque induced by the implanting physican by turningknob 38 is transmitted via coil 40 to torque transmission tool 44,without regard to the shape of solid stylet wire 30.

FIG. 7 shows the entire assembled lead with the two-piece stylet inplace. Notice that coil 40 fits coaxially within conductor coil 24 andsolid stylet wire 30 fits coaxially within the lumen of coil 40. In itsnormal position, as explained above, solid stylet wire 30 isforeshortened such that distal tip 34 does not reach the very distal tipof the lead. Torque transmitting tool 44 is inserted in torque receivingbody 28 at position 22 as explained in the Dutcher reference. Duringimplantation the solid stylet wire 30 is used to impart shape to themain body of the lead. Torque applied to knob 20 permits the physicianto control the implantation process. When the lead is properly affixed,knob 38 is turned, advancing helical fixation device 16 and causingpointed tip 18 to become securely lodged within the endocardial tissue.

Having thus described the preferred mode of practising the presentinvention those of ordinary skill in the art will be readily able toapply this present invention to other similar applications.

What is claimed is:
 1. A body implantable lead comprising:a conductorhaving a proximal end and a distal end and having a lumen extending fromsaid proximal end to said distal end; an insulating sheath covering saidconductor; fixation means for securing said distal end of said conductorto body tissue; electrical connector attached to said proximal end ofsaid conductor for electrically coupling said conductor to an electricalgenerator; stylet means removably located within said lumen of saidconductor for imparting a curve to a portion of the distal end of theconductor for guiding placement of said distal end of said conductor;and flexible means, having a proximal end, rotatably and removablylocated within said lumen of said conductor coaxial to said stylet meansfor transferring torque induced at said proximal end of said flexiblemeans to said fixation means while said stylet means imparts a curve tothe distal end portion of said conductor.
 2. A body implantable leadaccording to claim 1 wherein said stylet means is inserted coaxiallywithin said flexible means.
 3. A body implantable lead according toclaim 2 wherein said fixation means is a helically wound fixation coilhaving a sharpened tip whereby said fixation means may be screwed intosaid body tissue.
 4. A body implantable lead according to claim 1 or 2or 3 wherein said stylet means is a solid stylet wire having a proximalend.
 5. A body implantable lead according to claim 4 wherein saidflexible means has a proximal end and a distal end and has a lumenextending from said proximal end to said distal end.
 6. A bodyimplantable lead according to claim 5 wherein said flexible meansfurther comprises a knob fixedly attached to said proximal end of saidflexible means.
 7. A body implantable lead according to claim 6 whereinsaid flexible means is of a coil of body compatible metal.
 8. A bodyimplantable lead according to claim 6 wherein said flexible means is ofa body compatible plastic.
 9. A body implantable lead according to claim7 wherein said stylet means further comprises a knob fixedly attached tosaid proximal end of said stylet wire.
 10. A body implantable leadaccording to claim 8 wherein said stylet means further comprises a knobfixedly attached to said proximal end of said stylet wire.
 11. A bodyimplantable lead comprising:a conductor having a proximal end and adistal end and having a lumen extending from said proximal end to saiddistal end; an insulative sheath covering said conductor; an electrodecoupled to the distal end of said conductor; electrical connector meansattached to said proximal end of said conductor for electricallycoupling said conductor to an electrical generator; stylet meansremovably located within said lumen of said conductor for imparting acurve to a portion of the distal end of the conductor to guide theelectrode to a desired position in the heart; and flexible means, havinga proximal end, rotatably and removably located within the lumen of saidconductor coaxial to said stylet means for transferring torque inducedat said proximal end of said flexible means to the distal end of saidconductor while said stylet means imparts a curve to the distal endportion of said conductor.
 12. A body implantable lead according toclaim 11 wherein said stylet means is inserted coaxially within saidflexible means.
 13. A body implantable lead according to claim 11 or 12wherein said stylet means is a solid stylet wire having a proximal end.14. A body implantable lead according to claim 13 wherein said flexiblemeans has a proximal end and a distal end and has a lumen extending fromsaid proximal end to said distal end.
 15. A body implantable leadaccording to claim 14 wherein said flexible means further comprises aknob fixedly attached to said proximal end of said flexible means.
 16. Abody implantable lead according to claim 15 wherein said flexible meansis of a coil of body compatible metal.
 17. A body implantable leadaccording to claim 15 wherein said flexible means is of a bodycompatible plastic.
 18. A body implantable lead according to claim 16wherein said stylet means further comprises a knob fixedly attached tosaid proximal end of said stylet wire.
 19. A body implantable leadaccording to claim 17 wherein said stylet means further comprises a knobfixedly attached to said proximal end of said stylet wire. .Iadd.
 20. Abody implantable lead assembly comprising a lead having a proximal endand a distal end, said proximal end adapted to be connected toelectrical means for supplying or receiving electrical pulses, saiddistal end being adapted to be connected to tissue of a living body,said lead comprising a sheath of material inert to body materials orfluids and at least one wire conductor having a proximal end and adistal end and extending from said proximal end of said lead within saidsheath to said distal end of said lead, a terminal structureelectrically coupled to said proximal end of said wire conductor andadapted to electrically couple said proximal end of said wire conductorto said electrical means, an electrode assembly including an electrode,said distal end of said wire conductor being electrically connected tosaid electrode, said electrode including a tubular body which has aproximal end and a distal end and said sheath being coupled to saidproximal end of said tubular body and having a proximal end and a distalend, a corkscrew shaped securing device within said tubular body andhaving a proximal end and a distal end, a mounting member being receivedin said tubular body and having said proximal end of said securingdevice mounted on one end thereof, flexible drive means for rotationwithin said sheath, having a proximal end and a distal end extendingfrom said proximal end of said lead to said distal end of said lead,being coupled at its distal end to the proximal end of said mountingmember in said tubular body, said flexible drive means defining a lumenor cylindrical envelope about the central area of said lead throughwhich and in which a stylet is adapted to be received, and a drivemember at the proximal end of said lead fixed for rotation, said drivemember having two ends and having one end thereof connected to theproximal end of said flexible drive means and the other end thereofextending from said lead assembly, said drive member further beingadapted to be rotated to screw said securing device into living tissueand having a passageway therethrough opening into said lumen at one endand to the environment at the other end and into which passageway astylet is adapted to be inserted for passage through said drive meansfor stiffening said lead, and said flexible drive means enabling one torotate said corkscrew shaped securing device without twisting a curveddistal portion of said lead. .Iaddend. .Iadd.
 21. A body implantablelead comprising:a conductor having a proximal end and a distal end andhaving a lumen extending from said proximal end to said distal end; aninsulating sheath covering said conductor; fixation means for securingsaid distal end of said conductor to body tissue; electrical connectormeans attached to said proximal end of said conductor for electricallycoupling said conductor to an electrical generator; stylet meansremovably located within said lumen of said conductor for imparting acurve to a portion of the distal end of said conductor for guidingplacement of said distal end of said conductor; and flexible means,having a proximal end and a distal end, rotatably located within saidlumen of said conductor coaxial to said stylet means for transferringtorque induced at said proximal end of said flexible means to saidfixation means while said stylet means imparts a curve to the distalportion of said conductor. .Iaddend. .Iadd.
 22. A body implantable leadaccording to claim 21 wherein said stylet means is inserted coaxiallywithin said flexible means. .Iaddend. .Iadd.23. A body implantable leadaccording to claim 21 or claim 22 wherein said fixation means is ahelically wound fixation coil having a sharpened tip whereby saidfixation means may be screwed into body tissue. .Iaddend.